U.S. patent application number 12/942252 was filed with the patent office on 2011-03-10 for antenna feeding network.
This patent application is currently assigned to CELLMAX TECHNOLOGIES AB. Invention is credited to Greger Lenart, Jens Malmgren.
Application Number | 20110057856 12/942252 |
Document ID | / |
Family ID | 32294316 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110057856 |
Kind Code |
A1 |
Lenart; Greger ; et
al. |
March 10, 2011 |
ANTENNA FEEDING NETWORK
Abstract
An antenna feeding network, including at least one antenna
feeding line, each antenna feeding line comprising a coaxial line
having a central inner conductor and a surrounding outer conductor.
The outer conductor (4) is made of an elongated tubular compartment
(5) having an elongated opening (6) along one side of the
compartment (5), and that the inner conductor (3) is suspended
within the tubular compartment (5) by means of dielectric support
means (7).
Inventors: |
Lenart; Greger; (Taby,
SE) ; Malmgren; Jens; (Stockholm, SE) |
Assignee: |
CELLMAX TECHNOLOGIES AB
Taby
SE
|
Family ID: |
32294316 |
Appl. No.: |
12/942252 |
Filed: |
November 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12619433 |
Nov 16, 2009 |
7830328 |
|
|
12942252 |
|
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|
11578302 |
Dec 13, 2006 |
7619580 |
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12619433 |
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Current U.S.
Class: |
343/850 |
Current CPC
Class: |
H01P 3/10 20130101; H01Q
9/16 20130101; H01Q 19/108 20130101; H01Q 21/0006 20130101; H01P
3/06 20130101 |
Class at
Publication: |
343/850 |
International
Class: |
H01Q 1/50 20060101
H01Q001/50 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2004 |
SE |
0400975-9 |
Apr 15, 2005 |
SE |
PCT/SE2005/000548 |
Claims
1. An antenna feeding network (1) comprising at least one antenna
feeding line, each feeding line comprising a coaxial line (2)
having an inner conductor (3) and a surrounding outer conductor
(4), the outer conductor being made of an elongated tubular
compartment (5) having an elongated opening (6), and wherein the
inner conductor (3) is suspended within the tubular compartment (5)
by means of dielectric support means (7), wherein the center
conductor (3) has a varying cross-section.
2. The antenna feeding network (1) according to claim 1 wherein the
inner conductor (3) has a circular cross-section of varying
diameter.
3. The antenna feeding network (1) as in claim 1 or 2, wherein two
or more inner conductors (3) of adjacent compartments (5) are
connected to each other by cross-over elements (8) inserted through
openings in a wall between the adjacent compartments (5).
4. The antenna feeding network (1) according to claim 3, wherein
the compartments (5) are covered by means of a conductive cover (9)
over the cross-over elements (8).
5. The antenna feeding network (1) according to claim 3, wherein
the compartments (5) are covered by means of a conductive cover (9)
over the whole length of the elongated openings (6).
6. The antenna feeding network (1) according to claim 4, wherein
the conductive cover (9) is connected to the outer conductor
(4).
7. The antenna feeding network (1) according to claim 5, wherein
the conductive cover (9) is connected to the outer conductor
(4).
8. The antenna feeding network (1) according to claim 4, wherein
the conductive cover (9) is electrically isolated from the
compartments (5) by an insulating layer.
9. The antenna feeding network (1) according to claim 5, wherein
the conductive cover (9) is electrically isolated from the
compartments (5) by an insulating layer.
10. The antenna feeding network (1) according to claim 1 or 2,
wherein the side of the compartments (5) having the elongated
opening (6) is covered by means of an environmental protection
cover.
11. The antenna feeding network (1) according to claim 1 or 2,
wherein the compartments of the coaxial lines together with the
reflectors are forming a self-supporting framework.
12. An antenna reflector (10) comprising a plurality of adjacent
elongated tubular compartments (5) each having an elongated opening
(6) and forming an outer conductor (4) of a coaxial antenna feeding
line (2) at least one antenna feeding line having an inner
conductor (3) suspended within the tubular compartment (5) by means
of dielectric support means (7), wherein the center conductor (3)
has a varying cross-section.
13. The antenna reflector (10) according to claim 12 wherein the
inner conductor (3) has a circular cross-section of varying
diameter.
14. The antenna reflector (10) as in claim 12 or 13 wherein two or
more inner conductors (3) of adjacent compartments (5) are
connected to each other by cross-over elements (8) inserted through
openings in a wall between the adjacent compartments (5).
15. The antenna reflector (10) according to claim 14, wherein the
compartments (5) are covered by means of a conductive cover (9)
over the cross-over elements (8).
16. The antenna reflector (10) according to claim 14, wherein the
compartments (5) are covered by means of a conductive cover (9)
over the whole length of the elongated openings (6).
17. The antenna reflector (10) according to claim 15, wherein the
conductive cover (9) is connected to the outer conductor (4).
18. The antenna reflector (10) according to claim 16, wherein the
conductive cover (9) is connected to the outer conductor (4).
19. The antenna reflector (10) according to claim 15, wherein the
conductive cover (9) is electrically isolated from the compartments
(5) by an insulating layer.
20. The antenna reflector (10) according to claim 16, wherein the
conductive cover (9) is electrically isolated from the compartments
(5) by an insulating layer.
21. The antenna reflector (10) according to claim 12 or 13, wherein
the side of the compartments (5) having the elongated opening (6)
is covered by means of an environmental protection cover.
22. The antenna reflector (10) according to claim 12 or 13, wherein
the compartments of the coaxial lines together with the reflectors
are forming a self-supporting framework.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/619,433 `Antenna Feeding Network` filed on
16 Nov. 2009, which is a continuation of U.S. patent application
Ser. No. 11/578,302 `Antenna Feeding Network` filed on 13 Dec. 2006
now U.S. Pat. No. 7,619,580, which is a U.S. National Phase
Application under 37 CFR 371 of PCT Application Ser. No.
PCT/SE2005/000548 filed on 15 Apr. 2005, which is a PCT application
of Swedish patent application SE 0400975-9 filed on 15 Apr. 2004,
all of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention refers to an antenna feeding network
for a multi-dipole base station antenna.
[0004] 2. Description of the Related Art
[0005] A typical communications antenna consists of a number of
radiating elements, a feeding network and a reflector. The purpose
of the feeding network is to distribute a signal from a single
connector to all dipoles. The feeding network usually consists of
controlled impedance transmission lines. The antenna needs to be
impedance matched to a pre-defined value, usually 50 ohm or 75 ohm,
otherwise power fed into the antenna will be reflected back to its
source instead of being radiated by the dipoles, with poor
efficiency as a result.
[0006] The signal needs to be split between the dipoles in a
transmission case, and combined from the dipoles in a reception
case, see FIG. 1. This is usually done using the same network,
which is reciprocal. If the splitters/combiners consist of just one
junction between 50 lines, impedance match would not be maintained,
and the common port would be 25 ohm instead of 50 ohm. Therefore
the splitter/combiner usually also provides an impedance
transformation circuit that gives 50 ohm impedance at all three
ports.
[0007] Some manufacturers use coaxial lines with square
cross-section tubes, as an outer conductor, together with a
circular central conductor, as an inner conductor. The impedance of
the line depends on the ratio between the outer conductor and the
inner conductor, and what type of dielectric material that is used,
see FIG. 2.
[0008] Connections between the lines, here called "cross-overs",
are usually made using holes between the lines, and impedance
matching is done by varying the diameter of the inner conductor. In
such a way, the impedance transformation necessary for the
splitter/combiner can be realized.
[0009] The inner conductor is suspended in the square tubes using
small pieces of dielectric support means, for example
polytetrafluoroethylene (PTFE). These dielectric support means are
made as small as possible in order to maintain the line impedance.
The necessary impedance transformation is obtained by
machining.
[0010] Also losses within the antenna must be kept to a minimum in
order to obtain a high system receiver sensitivity, and
transmitting efficiency. Losses in the antenna are mainly due to
impedance mismatch or losses in the antenna feeding network.
[0011] The inherent problem with all these technologies is that all
dielectric support means except air introduce losses. Also, with
those technologies, large dimensions of network are difficult to
realize. Two things are needed to minimize losses in the feeding
network. Firstly the dimensions of the transmission lines must be
as large as possible in order to reduce resistive losses. Secondly
the dielectric, used in the lines, shall have low losses.
[0012] One drawback with this design is that the inner conductor,
that forms the central conductor, must be machined which is a
costly process. Also, tuning is tedious, as it has to be done by
re-machining the inner conductor.
[0013] Another drawback is that the connections between the lines
are made using holes between the compartments, which also make
assembly tedious, and it is difficult to inspect the result. It is
also difficult to maintain the correct impedance. Bad assembly
introduces intermodulation.
SUMMARY OF THE INVENTION
[0014] Present invention refers thus to an antenna feeding network,
including at least one antenna feeding line, each antenna feeding
line comprising a coaxial line having a central inner conductor and
a surrounding outer conductor, and is characterised in, that the
outer conductor is made of an elongated tubular compartment having
an elongated opening along one side of the compartment, and that
the inner conductor is suspended within the tubular compartment by
means of dielectric support means.
[0015] In the following present invention is described in more
detail, partly in connection with a non-limiting embodiment of the
invention together with the attached drawings, where
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a schematic view of the antenna feeding
network.
[0017] FIG. 2a shows a coaxial line in a cross-section view of
prior art.
[0018] FIG. 2b shows a coaxial line in a longitudinal cross-section
view of prior art.
[0019] FIG. 3a shows a coaxial line of present invention with an
elongated opening in a cross-section view.
[0020] FIG. 3b shows a coaxial line of present invention in a
longitudinal cross-section view.
[0021] FIG. 4a shows a top view of the connection between two
coaxial lines of present invention.
[0022] FIG. 4b shows a cross-section view of the connection between
two lines of present invention.
[0023] FIG. 5a shows a top view of an elongated tubular compartment
including the conductive cover of present invention.
[0024] FIG. 5b shows a cross-section view of an elongated tubular
compartment including the conductive cover of present
invention.
[0025] FIG. 6 shows schematically coaxial lines serving as a
reflector for the dipoles.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] FIGS. 1 and 3 show present invention that refers to an
antenna feeding network 1. FIG. 1 shows a typical antenna where the
thicker lines represent transmission lines, also called feeding
lines. These feeding lines are usually realized using coaxial lines
2. Each coaxial line 2 comprises a central inner conductor 3 and a
surrounding outer conductor 4 with some kind of dielectric support
means 7 in between, see FIG. 3. The material in the dielectric
support means 7 could preferably be a polymer, such as PTFE.
[0027] According to present invention the outer conductor 4 is made
of an elongated tubular compartment 5 having an elongated opening 6
along one side of the compartment 5, and the inner conductor 3 is
suspended within the tubular compartment 5 by means of dielectric
support means 7, see FIG. 3 and compare with FIG. 2 where there is
no elongated opening 6.
[0028] FIG. 3 further shows that the dielectric support means 7 and
the inner conductor 3 are insertable into the elongated tubular
compartment 5 from the ends of the compartments 5 Thus, having an
opening in the outer conductor helps to easily move the dielectric
support means 7 and improve the matching of the antenna. As the
opening 6 is parallel with the electrical currents, there is little
impact on the impedance of the coaxial line. Instead of machining
the inner conductor 3 for changing its impedance dielectric support
means 7, in the form of cylindrical pieces, are used and as
mentioned preferably made of the polymer material PTFE. These
support means 7 serve two purposes. Firstly the support means 7 are
used to maintain the inner conductor 3 in the middle of the
compartment 5. Secondly the support means 7 are used to match the
transmission lines.
[0029] The dielectric support means 7 are preferably spacedly
positioned along the inner conductor 3. The dielectric support
means 7 are movable on the inner conductor 3, within the elongated
tubular compartment 5. Further, the dielectric support means 7 are
positioned at the desired position on the inner conductor 3 and
will be fastened at desired locations therein.
[0030] FIGS. 4a-b show the inner conductors 3 of adjacent
compartments 5. Where two lines need to be connected, the wall
between the two compartments is removed along a short distance. A
cross-over element 8 is then placed in this opening, and connected
to the lines on each side of the wall. The cross-over is designed
in such a way, in conjunction with the dimensions of the coaxes and
the opening between the two coaxes, that the characteristic
impedance is preserved. The cross-over element 8 may be connected
to the lines by different methods, for example by means of screws,
soldering, gluing or a combination thereof, see FIGS. 4a-b. The
inner conductors 3 are easily accessible from the top. This makes
assembly considerably easier.
[0031] FIGS. 5a-b show the compartments 5 at the cross-over element
8 that is covered by a conductive cover 9. Because currents are no
longer parallel with the lines 2 near the cross-over, covering the
cross-over element 8 with a small-sized metallic surface makes
currents travel also in a direction perpendicular to the lines 2.
The rest of the lines 2 do not need a conductive cover 9.
[0032] In one embodiment the antenna uses different diameters of
the inner conductor 3 to achieve impedance matching.
[0033] In another embodiment the antenna uses a combination of
different inner conductor diameters and dielectric cylinders to
achieve impedance matching, see FIG. 5b.
[0034] In another embodiment a cover 9 consists of a metallic cover
along the whole of the elongated opening 6 of the compartment
5.
[0035] In yet another embodiment there is a metallic conductive
cover 9 covering the cross-over element 8. The rest of the lines 2
do not need a conductive cover 9, but can be covered by means of an
environmental protection cover made in an inexpensive material such
as, but not limited to, plastic.
[0036] In another embodiment the conductive cover 9 can be
electrically connected to the outer conductor 4, or it can be
isolated from the outer conductor 4 using a thin isolation
layer.
[0037] FIG. 6 shows the feeding network 1, in detail the
compartments 5 of the coaxial lines 2, that is used as a reflector
10 for dipoles 11 in a communication antenna 14. The compartments
of the coaxial lines together with the reflector form a
self-supporting framework. Hence it is no longer necessary to have
a separate frame.
[0038] Above, several embodiments of antenna feeding network have
been described. However, present invention can be used in any
configuration of antenna feeding network where the impedance losses
and matching can be compensated for by a coaxial line according to
the invention.
[0039] Thus, the present invention shall not be deemed restricted
to any specific embodiment, but can be varied within the scope of
the claims.
* * * * *